Elastography provides new opportunities in diagnostic imaging for the visualization of normal and abnormal tissues, including cancer This is done by imaging normal distributions as well as abnormal changes in tissue elasticity that occur in many tissues. Our overall hypothesis of this PPG renewal application is that cross-sectional strain images (elastograms) that are related to the local elastic properties of soft tissues, convey important new information that could substantially increase the capability to display and interpret normal and abnormal tissue structure. The overall goal of this program project proposal is therefore to explore and evaluate the way by which elastography may best be utilized to increase this capability, especially in areas of breast and prostate cancer. This PPG competitive renewal application consists of individual research projects (with subcontracts) and cores; an industrial partner is also included. PROJECT: The study of tissue displacement and inverse problem methods (M. Bertrand), with applications to the imaging of the prostate (via subcontract with JY Chapelon) PROJECT: The study of tradeoffs in elastographic image formation and elastographic texture (J. Ophir), and for the basic elastic properties of breast and prostate tissues (via a subcontract with T. Krouskop) PROJECT: Clinical validation of elastograms in the breast in vivo (B. Garra and C. Merritt) and in liver and prostate in animal models (sib subcontract with C. Merritt) CORE: Program Administration Core (J. Ophir) CORE: Hardware and Software Development and Maintenance Core (F. Kallel) CORE: Inter-laboratory Communications Core (M. Bertrand) INDUSTRIAL PARTNER: ATL Ultrasound Corp. has agreed to supply the PPG participant with four state- of-the-art ultrasound equipment and training (R. Daigle)